There does exist many types of submersible pumps for groundwater sampling and other uses. FIG. 1 shows, generally at 100, a typical prior-art configuration. Since devices of this kind are inserted down well holes, the unit consists of an outer cylindrical pump body 102, typically constructed of stainless steel. The body includes a lower inlet end 104 and an upper outlet end 106. An internal cylindrical bladder 108, typically constructed of Teflon, partitions the interior of the pump body 102 into a gas-carrying section 110, and a fluid-carrying section 112 within the bladder 108.
A tube 114 having, perforations 116, is generally positioned within the fluid-carrying section 112, as shown. A lower check valve 120 is provided at the lower inlet end 104 to permit groundwater or like fluids to pass through the lower end 104 and into the tube 114 and fluid-carrying chamber 112 through perforations 116. The check valve 120 also prevents the fluid from backflowing through the lower inlet 104. An upper check valve 122 allows fluid from the fluid-carrying chamber 112 to be discharged through the upper end 106 by passing through apertures 116 and into the tube 114. The upper check valve 122 also prevents the fluid from backflowing down into the pump interior.
Above ground, a controller 130 is provided having a conduit 132 in pneumatic communication with the gas-carrying section 110 within the pump body 102. The apparatus operates by pressurizing and venting the gas within the chamber 110, thereby compressing and expanding the bladder 108, which is quite flexible, thereby forcing fluid within the chamber 112 out the upper end 106 through tube 114 by way of apertures 116. More particularly, when the pump body is submerged, ground water or other fluid flows into the chamber 112 through tube 114 having apertures 116 through the lower end 104, bypassing check valve 120 due to natural hydrostatic pressure.
When an actuating gas such as compressed air is driven through conduit 132 and into the gas-carrying section 110, the bladder 108 is compressed and the lower check valve 120 is forced against the opening 104, thereby forcing the fluid contained within the fluid-carrying section upwardly and out through the upper opening 106, displacing check valve 122 in its path. The gas-carrying chamber 110 is then vented at ground level through controller 130, permitting a fresh charge of ground water to again fill the fluid-carrying chamber 112 and tube 114 through perforations 116, at which time another cycle may be started by compressing the bladder 108.
Although a single controller 130 may be configured to control a multiplicity of similar pumps, the timing sequences for each pump must be optimized and stored to ensure the most efficient operation for each sampling station. The timing/cycling means within the controller therefore typically includes a 3-way valve associated with each pump to which it is connected. The 3-way valve is alternatively actuated and de-actuated to produce a pulsating flow to the bladder of each pump, wherein a compressed gas is applied via each conduit 132, on which the 3-way valve changes state, enabling the gas contained within chamber 110 to be vented to atmosphere. The controller 130 must therefore include electronic, pneumatic or mechanical timing devices associated with each 3-way valve, in each pump, to ensure proper operation thereof.
Pumps of the type just described are used in a variety of applications, including the continuous collection of gasoline and other hazardous materials from aquifers, as well as occasional groundwater sampling. There is also a need for pumps used for more infrequent sampling, using a device sometimes referred to as a "bailor." Originally, such devices assumed the form of a polyethylene or Teflon tube having a bottom end with a check ball. The device was lowered into a well, allowing liquid to trickle past the check ball until the tube was filled and the check ball was seated. The device was then removed form the well, the sample removed, and the rest of the device discarded.
By EPA mandate, the bailing process must remove three times the volume of a well before a sample is taken. This means that if the volume of the well is 50 gallons, 150 bailing operations must be taken prior to taking the actual sample. The time-consuming nature of this process led to the development of continuously cycling sampling pumps of the type described with reference to FIG. 1. Even with these, however, the apparatus is expensive, and the bladder must be removed, typically requiring a meticulous dismantling of the pump body. The need therefore remains for an economical pump capable of repetitive sampling. Ideally, such a pump would include some form of collection cartridge that is easily removable, allowing the pump to be used for more infrequent sampling applications, including bailing.